Apparatus for continuous castings



Oct. 31,v 1950 N. P. (5088 2,527,545

APPARATUS FOR CONTINUOUS CASTINGS Filed May 2, 1947 2 Sheets-Sheet 1 3740 INVENTOR NORMAN F. G055 fi a BY Md 74117 61 Fig-3 A ATTORNEYS.

Oct. 31, 1950 N. P. soss APPARATUS FOR CONTINUOUS CASTINGS 2Sheets-Sheet 2 Filed May 2, 1947 is m w 5 P R. V 0 Z 1 Patented Oct. 31,1950 UNITED STATES PATENT OFFICE APPARATUS FOR CONTINUOUS CASTINGSNorman P. Goal, Mayfield Heights, Ohio Application May 2, 1947, SerialNo. 745,569

' s Claims. (01. 22-512) 1 This invention relates to improvements in theart of continuously casting metal.

One of the objects of the present invention is ,to provide a novel dieopen at both ends with means for holding the sections always in alinedposition, thus avoiding the distortion generally brought about byheating of the die. The construction also provides for expansion of thedie in the general direction of metal travel so as to prevent distortionof the die due to localized heating and expansion.

Another object of the invention is the sudden or sharp increase in thecross sectional dimensions of the die at a point in the travel of themetal through the die, with the provision at that point of means forintroducing lubricant between the surface of the formed metal and theadiacent die wall.

Another object of the invention is the provision of a slight sharpshoulder at any zone in the die passageway whereby at a predeterminedhorizontal level the cross sectional dimension of the die is increased,substantially entirely around the die, so as to momentarily release thecontact between the skin of the congealing metal and the die wall.

Still another object of the present invention is to provide a die havingwalls completely surrounding a vertical passageway wherein the side andend walls of the die are separate wall portions and there being slightshoulders extending in a horizontal line entirely around all of the wallportions when they are assembled together in the die. 1 My inventionalso provides gravity actuated feed for feeding lubricant under constantpressure to the zone between the outer skin of the metal being formedand the adjacent die wall. I also provide a means for centering the castmetal in the die, utilizing varying, pressure on the lubricant feedingdevices for this purpose.

Other objects and advantages of my invention will be apparent from thaccompanying drawthrough one embodiment of my improved apparatus:

Fig. 2 is a transverse sectional view taken along the line 2-2 of Fig.1;

Fig. 3 is an enlarged fragmental sectional view illustrating a portionof the interior surface of the die in the first chilled section;

Fig. 4 is an enlarged and exaggerated sectiona view of a portion of Fig.1 illustrating a stepped construction of the die wall; I

Fig. 5 is an enlarged fragmental sectional view illustrating amodification of Fig. 3;

Fig 6 is an enlarged and exaggerated sectional view of a modification ofFig; 4 illustrating a stepped construction of the die wall both at thejoints between die sections and at points in the intermediate portion ofa section;

Fig. '7 is a fragmental perspective view showing a modification of myinvention wherein the stepped construction is applied to a differentform of die;

Fig. 8 is a sectional view enlarged taken along the line 8-8 of Fig. 7;while Fig. 9 is a sectional view taken along the line 8-9 of Fig. 8.

In the device of Figs. 1 and 2, molten metal I0 is held in a ladle i Igenerally of the foundry type and so formed of refractory material thatthe metal remains molten for the time necessary to teem the same intothe casting die. The pouring lip of the ladle is mounted on a fixedpivot 12 and by means of the upward pull on cable 13 the rate of flow ofthe metal ma be readily controlled. Preferably a partition wall Ila isprovided to hold back slag and the like so that clean metal may bepoured. An electrical heating element it of the glow bar type isprovided to keep the metal molten at the pouring lip.

Means is provided for introducing the molten metal into the open upperend of the casting die without turbulence and in a manner to preventformation of air pockets in the upper end of the die. To this end meansis provided for holding a small pool or reservoir I! of molten metaljust prior to the flow of the metal into the die. Suitable refractorymaterial It is provided to hold this pool, the refractory material beingmounted on suitable supports ii. The refractory material is so formed atthe point [to as to provide a dam over which the molten metal flows justprior to entering the pre-forming chamber Hi. This dam is heated by aglow bar is and other glow bars 20 are provided for insuring thefluidity of the metal in pool ill. The pre-forming chamber i8 has walls2| of ceramic material adapted to with- 3 stand high temperatures suchas those encountered when dealing with molten steel. The side wall Maand one parallel thereto (not-shown) extend full height to the level Mb.The side nearer the pool 16 is cut away at lie to provide easy entranceof the molten metal over the dam a and into the top of the pre-formingchamber. The side opposite this is cut away a indicated at lid 'toprovide a slag overflow port from which a run-off channel 22 extends.Refractory material completely surrounds the pre-forming chamber asindicated at 23. Glow bar devices 34 are provided tomaintain aneventemperature around the pre-forming chamber, while a g1owbar 25 isarranged in a recess directly above the,

open end of the casting die to insure molten metal at this point.

It should be understood that the cross section of the casting die may beof any desirable form, but for simplicity I have here shown a die forcasting a square bar, as shown at 26 in Fig. 2. The cross section of thepre-forming chamber I3 is of almost exactly the same section, butpreferably the pre-forming chamber is slightly less in width than thefirst forming chamber immediately beneath it, as will later appear.

The chilled die is comprised preferably of a plurality of short sections31a, 21b, 21c and 21d, as shown in Fig. 1. I prefer to build thesesections of short strong construction, say not much over nine toeighteen inches in vertical length, so as. to minimize distortion due tothe heating of the die walls in operation. These chilledsections of thedie may be alike and are of the form generally shown in section in Fig.2. Here the die section 210 is formed in two L-shaped portions, thedivision line between the same being indicated at 23 in Fig. 2. The diewalls are hollow, as indicated at 29 for the introduction of a coolingfluid.

such as water. Means (not shown) is provided individual to each of thesections 21a, 21b, etc., for the inlet and outlet of cooling fluid foreach section.

Means is provided for maintaining vertical alinement of the varioussections of the die. As shown in Fig. 2, four ears 30 are providedrespectively at the four corners of the die extending diagonally outwardand provided with openings 3011 through which pas the vertical aliningrods 3|. The lower ends of these rods are mounted in fixed position in astructure 32, which is a portion of the same structure comprising themembers l1 previously mentioned. The upper ends of the rods 3! entersuitable pockets 33 for holding the upper ends in alinement. It shouldbe understood that the ears 30 are a fairly snug fit but free to slidealong the rods 3|. Therefore the individual sections of the die are heldin vertical alinement but are free to move individually and collectivelydownward on the rods 3| as required when the various sections are heatedby the hot metal passing through the die.

Means is provided for holding the various sections of the die 21a, 21b,etc., in contiguous alined position, as shown in Fig. 1, while at thesame time permitting expansion in a vertical direction. The meansdisclosed for this purpose comprises a set of heavy springs 34 which arein compression between the fixed platform 32 and a plate 36 whichfinishes off the bottom end of the die. The springs 34 are strong enoughto-hold the various die sections in abutting relationship during thecasting of the metal, but the forces tending toward expansion due to theeffects of heat on the metal. of the die are sufficiently great tofurther compress the springs 34. By this arrangement I avoid distortionof the die walls which would normally take place if the die were held infixed position between immovable structures both top and bottom.

Means is provided for introducing lubricating material between the skinof the newly formed metal and the die walls. To this end ports 36 areprovided at various points along the length of the die and means isprovided to feed into these ports lubricating material preferably in theform of finely divided material having lubricating properties, such asgraphite, or such material may be provided in the form of a paste or aneasily friable briquette. Just outside each of the ports 36 I have showna feed hopper 31 attached to the wall of the die just above the port 36,as by means of bolts 33. It results from this construction that'as the.die sections expand due to heat, the feed hopper is always alined withits associated port 36. The finely divided lubricating material isplaced in one of the hoppers 31, the bottom of which opens into apassageway leading to one of the ports 33. Means is provided for feedingthis lubricating material under substantially constant pressure to theport 36. As here shown, such means comprises a plunger 38 having a snuglit in the passageway 31. A bell crank 40 pivotally mounted at 41 has ashorter arm 40a which has a pin and slot connection with the plunger 33.On the longer arm 40b of the bell crank is mounted an adjustable weight42. The action of gravity on this weight gives a substantially constantpressure on the lubricating material on the passageway 31 and forces itthrough the associated port 36 so as to fill the interstices between theskin of the forming metal and the adjacent die wall. Referring to Fig.2.

' the ports 36 are indicated in dotted lines as being substantiallycoextensive with the sides of the billet or bar 43 which is formed inthe die. Thus, lubricant is supplied along the full width of the bar 43around its entire periphery at each point where the ports 36 areprovided. It will be noted in Fig. 2 that there is a small square 44 ateach corner of the die wall between ports 36. It is these small squareportions at each corner which.

v the die will withstand less pressure than when it is cooled by furtherprogress down the die. Also, as is well understood, the metal, as itbecomes cooler, will contract more, allowing a. slightly greater spacebetween the skin of the metal and the interior wall of the die near thelower end of the latter.

Another form of lubricant may be supplied near the outlet end of thedie, as is illustrated directly beneath the die section 2102. Here fourports 46 are provided similar to the ports 36 above described. A blockof friable lubricating material 46 is placed in each port 46 and aplunger 41 in each port is used to apply pressure to the block oflubricating material actuated by a weight 42 on a bell crank 40, asdescribed in connection with the pressure applying means previouslydescribed.

As the metal emerges from the bottom of the die, it has a skin strongenough to support the metal in the center even though the latter has notyet completely solidified. It is preferable in the case of metals ofhigh melting point to supply water sprays 48 at this point to hasten thesolidincation of the metal. A pair of coacting pinch rolls 4! is usuallysupplied for withdrawing the formed metal from the die. The rolls shownin Fig. l have V-shaped surfaces forming a 90 angle on each roll 50 thatthe two rolls together embrace the four sides of the bar 43. In spite ofthe best efforts to withdraw the bar 43 with uniform lateral pressure,there is a tendency at times for the metal forming in the die to traveltoward one of the die walls oif center, thus tending to scrape andscratch against one side of the die.

It will be noted that no bulk lubricant is supplied to the metal in thesection 210 which is the chilled forming chamber which is below theceramic pre-forming chamber 18. If lubricant is freely supplied to steelin molten condition, it would either burn and disappear or it wouldchemically unite with the metal to carburize it. My theory of the actionwhich takes place at the upper end of the die is that solidificationbegins to occur at approximately the zone indicated at 55 near the topof section 21a. At first there is only a very thin skin formed on thecongealing metal, but as the metal progresses downwardly through sectionNo this skin becomes strong enough to shrink away from interior walls ofthe die and to exert some confining effect upon the congealing metal inthe center of the die. Where a skin of this thickness is formed, Idesire to begin the introduction of external lubricant as soon aspossible. To this end, I desire to form the section 21a relativelyshort. It may be as short as two inches when casting a steel billet fourinches by four inches in a mold four feet long.

Somewhere near the bottom of section 21a I believe that the hydrostatichead of the molten metal in the top of the die is tending to press thenewly formed skin of the congealing metal against the inner walls of thedie, while at the same time the contact of the hot metal with the colddie causes the congealing metal to tend to shrink away from the diewall. Therefore, at this point, which is at the lubricant feeding ports36 at the level 53 indicated in Fig. 4, I introduce a lubricant such asthe finely divided graphite shown at 51. As l'ater described inconnection with Fig. 4, the cross-sectional dimension of the dieincreases slightly as the metal passes from section 21a to section 21b.Thus at the zone 53 I suddenly relieve the friction of the congealingmetal pressing against the inner walls of the die while supplyinglubricant through the ports 38. and this aids greatly in moving thecongealing metal through the die.

According to the above explanation, there is a short distance in thesection 21a wherein it is desired that the newly forming metal shouldnot stick to the walls of the die but where it is impractical to supplythe type of lubricant furnished at the ports 36 later on. I havediscovered two ways for solving this problem. In Fig. 3 I haveillustrated in greatly exaggerated fashion a fragmental portion of theinterior surface of the die section 21a. wherein the surface 5| is incontact with the bar 43. I prefer to form the section 21a of a metalwith high heat conductivity, such as copper. This copper is given arough cut 5!, after which colloidal graphite 50 is applied to the roughsurface of the copper and forced into the pores of the copper btarnishing. I find that a surface formed in this fashion will retain itslubricating qualities next to molten or hot metal for a long period oftime, while at the same time interfering only slightly, if at all, withthe heat conducting qualities of the section 21a, which is water cooledthrough passageway 29, as previously mentioned. I believe that thesuccessful use of this thin layer of graphite 50 at this point rests onthe fact that there is practically no temperature gradient in thegraphite layer. In other words, the graphite is substantially at thesame temperature as the metal of the chilled section 21a and at this lowtemperature there is substantially no chemical reaction between the hotmetal and the graphite.

In Fig. 5 I have shown another method of treatin the interior surfacesof the die section 21a to obtain long life and satisfactory results.Here the interior wall of the section 21a is given a thin plating 58 ofa metal which is non-alloying with respect to the metal being cast. Inthe case of steel, a plating of silver is satisfactory. In the case ofcopper, the plating might be molybdenum. The plating 58, while not alubricant, nevertheless provides a non-wetting and non-sticking surfaceat this point.

I have stated earlier that I find it very important for the easy advanceof certain metals through my improved die to slightly increase theinternal dimensions of the die at several points along its length. InFig. 4 I have greatly exaggerated this condition for the sake ofillustration. The change in dimension between the ceramic pro-formingsection 2i and the top die section 21a at the level 52 is optional andmay be practically anything from zero to one-half inch increase inover-all dimension in the case of a steel billet approximately fourinches by four inches in section.

A change in the cross sectional area of the die is of greater importanceat the level 53 where the metal passes from section 21a to 211). Herethe increase in the cross-sectional dimensions of the die is preferablyof the order of one-thirty-second to one-eighth inch in the over-alldimension of a steel billet such as mentioned above. This structure maybe repeated at the levels 54 and 55 if desired. It results from thisconstruction that lubricant is supplied through ports 36, say at thelevel 53, where the cross-sectional area of the die suddenly increases.Thus the friction resisting the movement of the metal through the die issuddenly released at the level 53 and at the same time lubricant issupplied through the ports 36 between the skin of the metal and theinner wall of the die to insure good lubrication and protection of thedie walls.

I find that apparatus constructed as above described will continuouslycast a metal bar which is free of blow holes and free of slag if thelevel in the pre-forming chamber l 8 is occasionally raised to run offthe slag through the passageway 22. The hydraulic head provided by themolten metal in the preforming chamber is sufilcient to form a verydense metal in the first chilled section 21a and by pre-forming themetal in chamber [3 to substantially the cross section of the rest ofthe die, the metal enters easily into the chilled portion of the diebecause of the slight increase in sectional dimensions at the level 52.The metal movement is further facilitated in the rest of the die bymeans of the stepped constructions at the level 52, 53, 54, etc., and bythe introduction of lubricant through the ports 36. The result is acontinuous bar 43 of metal having a controlled crystalline structure andvery fine surface characteristics, as well as freedom from internalimperfections, as previously pointed out. At the same time, the shortstrong die sections 21a, 21b, etc., are subject to very littledistortion, are held in permanent alinement by the guide rods 3|, whilethe individual die sections may expand longitudinally as the ears 30slide along the guide bars 3|.

In Fig. 6, I have shown a view similar to Fig. 4 illustrating a modifiedconstruction including all of the features of Fig. 4 including thestepped back construction at the zones 52, 53' and 54 in all respectssimilar to that just described at 52, II, and 54. In addition, however,stepped back construction is shown at 59a in section 59, at 60a insection 60 and at GM in section 6|. At each of these points 59a. 60a andGla there is a horizontal shoulder extending entirely around theinterior die wall of the order of a few thousandths of an inch so as toslightly increase the crosssectional dimensions of the die as the metalpasses that horizontal zone on its travel downwardly. This steppedconstruction is necessarily exaggerated in Fig. 6 as it was in Fig. 4.Obviously, where the cross-section of the die is anywhere from twoinches to several feet, a shoulder of the order of say three thousandthsof an inch would not show on the drawings at all. While the drawinggives the impression of a taper, there is no such appearance in thefinished die. It appears to be of one cross-sectional dimension for itsentire length. There is a very important function performed by theslight offsets indicated at 52', 63, 54', 59a, 60a and Ma whether or notlubricant is introduced at the same zone where the shoulder occurs. Ihave discovered that the first outer skin which forms on the metal asits starts through the hollow die is very thin and easily ruptured. Suchan accident will spoil the surface of the steel and the quality of themetal in the interior of the section. In a mold section having the samecross-sectional dimension throughout the vertical passageway orgradually tapered so as to increase the cross-sectional dimension of thedie passageway as the metal moves downwardly, the f errostatic pressureof the molten interior continuously presses the tender outside skinagainst the die wall and this creates sufficient friction to hold up theeven movement of the metal through the die with consequent occasionalrupturing of the tender skin. By the use of the slight shouldersindicated, each time the die wall is sudden y increased incross-sectional dimension, the friction between the tender skin and thewall of the mold is suddenly relieved at all points around thehorizontal zone, and the advance of the congealing metal is facilitated.The shoulder dimension at the various points indicated should not be sogreat as to cause a breakage of the thin skin of the congealing metal.

Another advantage of the sudden increase in the sectional dimension ofthe die as indicated at the points 59a, 66a and Ma is due to thepeculiar action of the freshly formed skin of the congealing metal.Wherever this skin touches the cold die wall it tends to shrink away.However. the ferrostatic pressure of the molten interior tends to holdthe thin skin against the cold wall which often causes local cold spotsin the newly formed skin. At these points the congealing metal tends tocling to the die wall. By the use of m invention, the contact of theskin with the die wall is suddenly released at all points around a hori-I are provided of which only two are indicated at 62 in Fig. '7. The dieillustrated is for casting .a slab section which comprises a longer sidewall 63 and a shorter end wall 64. Each of these walls is formed by aplurality of sectional wall portions arranged vertically one above theother as ex plained in my above-mentioned copending application. Eachwall portion at its upper edge has radially extending ears 63a and 64aby means of which the wall portions are suspended in the corner posts.Each of the wall sections is hollow as shown in Figs. 8 and 9 and aprovision is made for supplying cooling water in the hollow centralportions 63b and 64b respectively.

In this modified form of die, the present invention is applied byforming a slight sharp shoulder 65 in the wall portion 63 and a similarshoulder 66 at the same horizontal level in the wall portion 64. It willbe understood that the opposite side and end wall portions have beenomitted for clearness, but similar shoulders are formed in these wallportions so that a continuous slight shoulder of the order of a fewthousandths of an inch is provided entirely around the four die walls atthe horizontal level selected. Therefore, in the zone 61 below theshoulders 65 and 66 the crosssectional dimensions of the die are a fewthousandths of an inch greater than in the zone 66 above the shoulders.It will be understood by those familiar with machining operations thatit would be very difficult to machine the shoulders 59a, 60a and Hz: inthe mid portion of an integral four-wall die section. In theconstruction shown in Fig. 7, however, an end mill may be utilized inthe zone 61 so as to accurately machine the portion 61 to leave anaccurate shoulder at the level Or at the level 66. If curved cornc-rs orfillets are provided at the points 69 as indicated, this may be done bygrinding an appropriate curved face on the end mill. Obviously. theshoulders 65 and 66 have been exaggerated in the drawings as it would beimpossible to show a few thousandths of an inch on the scale of thedrawing. With this form of my invention therefore, I am enabled toprovide the slight sharp shoulder with great ease and accuracy and thewall portions, when assembled, will exactly aline the shoulders 65 and66 by engagement of the ears 63a and 64a in the notches 62a of thecorner posts.

This application is a continuation in art of my copending applicationSerial No. 528,045, filed March 25, 1944, for Method and Apparatus forContinuous Casting, now abandoned.

What I claim is:

1. Apparatus for continuously forming metal comprising a die havingcooling walls completely surrounding a central vertically extendingpassageway through which metal passes downwardly as it congeals, and asharp shoulder of a few thousandths of an inch depth and extendingsubstantially uninterruptedly about the interior faces of said walls ata horizontal level and providing a slight but sudden increase incross-sectional dimensions of said passageway below said level.

2. Apparatus as in claim 1 wherein said die comprises vertically alinedsections, and said sharp shoulder is provided at a level intermediatethe top and bottom of one of said sections.

3. Apparatus as in claim 1 wherein said die comprises vertically alinedsections, and said sharp shoulder is provided at the level where two ofsaid sections meet.

4. Apparatus as in claim 1 including means for introducing a lubricantbetween said metal and said interior faces of said die walls at thelevel where said sharp shoulder is provided.

5. Apparatus as in claim 1 including means for introducing a lubricantbetween said metal 10 and said interior faces of said die walls belowthe level where said shar shoulder is provided.

NORMAN P. GOSS.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS 1 Number Name I Date 152,040 Lavroff June 16, 1874388,336 Boulton Aug. 21, 1888 2,225,373 Goss Dec. 17, 1940 2,276,657Junghans Mar. 17, 1942 15 2,284,704 Welblund et a1. June 2, 19422,363,695 Ruppik Nov. 28, 1944

